My weakness is plain and shiny metal, which just asks to be engraved. As it happens, I bought a CZ452 Varmint rifle some time ago and it had a bolt. It needed to be engraved.
So far I’ve engraved the part, which is seen when the bolt is in open position. Someday I’ll do the closed position area too. It was quite an interesting experience to engrave it, because it was round and of rather hard metal.